This invention relates to systems for producing, high voltage electrical power from fossil fuels or other non-electrical energy resources.
Electrical power generation plants have become larger as power consumption by industry and the public has increased. Where conventional power generation techniques are used, scaling up in size enables increased efficiency in the conversion of fuel energy to electrical energy and the unit cost of electric power is reduced. This gain in efficiency is largely confined to the generating station itself. Other external factors have recently arisen which greatly reduce any advantage which might be obtained by still further increases in generating station size.
The sources of fuels for operating power production plants are often remote from the power consuming area where the plant is located. Enormous quantities of coal, oil, gas, or the like must be transported long distances to supply large centralized generating stations. This is costly and inconvenient and requires an increasingly larger investment in railways, pipelines or the like. The fuel transportation operations are in fact more costly than appears at first consideration since less than one half of the thermal energy produced by burning fossil fuels in a large power plant is actually converted into electrical power. The remaining thermal energy must be disposed of. Thus, more than one half of the total fuel transportation cost is, in effect, wasted.
Another factor which inhibits the construction of still larger power plants near urban areas is the recent increased concern over adverse environmental effects which may occur at conventional power generating stations. In most cases, large quantities of combustion products and residual thermal energy must be disposed of in some manner. Apparatus for minimizing the release of pollutants and for reducing other undesirable environmental effects is costly and in many cases cannot be fully effective. Difficulties from environmental concerns are by no means confined to the generating station itself but arise also from fuel transportation facilities, such as pipelines, which are a necessary accompaniment of conventional power generation systems.
The problems discussed above can be greatly reduced by locating power plants near the mines, wells or other primary energy sources which are often situated in geographically remote regions away from the large urban areas where power is consumed. In the Western United States of America, for example, there are great reserves of coal, oil shale, tar sands, geothermal energy and the like situated in sparsely populated remote regions. While there have been instances where power generating facilities have been located at primary energy sources, notably in connection with hydro-electric facilities, there are several considerations which have heretofore tended to inhibit the location of power plants at fuel resource sites.
The investment required for a massive power generating station located at a remote mine, oil field or the like can only be justified if the fuel reserves in the immediate area are extremely large and will not be exhausted during the life of the plant. Concentrations of fossil fuels justifying this investment are relatively scarce, and it is much more common to find reserves of energy resources distributed over a broad area and not in concentrations which would justify a massive permanent power plant. In connection with certain forms of energy resources, even fairly concentrated sources may not be suitable for supplying a centralized massive power plant. Geothermal steam, for example, can only be moved for short distances through pipelines because of heat losses.
Another factor which has inhibited the location of power plants at fuel resource sites is the limitations of existing high voltage transmission lines. In general, transmission line losses are reduced by operating at higher voltages but a practical limit has been reached in raising voltages using conventional technology.
If alternating current is utilized, as is the case with most existing utility systems, massive extremely costly transformers are required to couple power generators to the high voltage line at the production end of the system and to step down the voltage at the distribution end. To reduce capacitive losses where voltage is raised, transmission lines must be suspended high above the ground. In addition, phase synchronization between generating stations connected to the same line is costly and imposes technical problems.
It has heretofore been proposed to reduce these power collection, transmission and distribution problems by converting to DC power transmission systems. DC systems have not been extensively used in part because of the cost and technical problems involved in converting high voltage DC power to low voltage AC power at the distribution end of the system. Further, use of DC transmission lines does not eliminate the need for costly massive transformers if conventional techniques are relied upon. Most DC power producing devices, whether generators, fuel cells, magnetohydrodynamic devices or others, do not produce very high DC voltages insofar as a single unit is concerned and it has not usually been practical to couple such devices directly to a high voltage DC power transmission line. The output of the DC generator or other DC power production device can be caused to drive an AC generator to produce AC power which may be stepped up in voltage by a transformer for coupling to the DC transmission line through a rectifier but this seemingly makes massive costly high voltage transformers necessary even in a DC power transmission system if conventional techniques are employed.